A so-called hydrostatic transmission (HST) is generally installed in a work vehicle such as a wheel loader and the like. In a HST type of work vehicle, a hydraulic pump is driven by an engine and a hydraulic motor for traveling is driven by hydraulic fluid discharged from the hydraulic pump. As a result, the work vehicle travels. Vehicle speed and tractive force can be controlled in this type of HST work vehicle by controlling the engine rotation speed, the displacement of the hydraulic pump, and the displacement of the hydraulic motor for traveling (see International Publication WO 2002/050454).
The work vehicle also includes a parking brake. The parking brake is activated by an operator operating a parking brake operating member such as a parking switch. Normally, the operator decelerates the work vehicle by using a foot brake and the like and operates the parking brake when the work vehicle is in a stopped state. As a result, the work vehicle is made so as not to move from the stopped position.